The ravaged Great Mosque of al-Nuri, as seen through rubble in the Old City of Mosul on Thursday. Iraqi forces say they've recaptured the landmark, where ISIS leader Abu Bakr al-Baghdadi declared the group's "caliphate" in 2014.

Ahmad al-Rubaye
/ AFP/Getty Images

Nearly three years to the day after the leader of ISIS declared the "caliphate" of Iraq and Syria from the pulpit of Mosul's Great Mosque of al-Nuri, the historic structure is back in Iraqi hands.

A military spokesman announced Thursday that Iraqi troops successfully stormed the centuries-old religious landmark, reclaiming the ruins of a building destroyed by ISIS militants last week.

The moment marks a major symbolic victory for an Iraqi military that watched in 2014 as ISIS leader Abu Bakr al-Baghdadi ushered in a new, bloody era in the country, which was reeling from the Islamic State's territorial gains.

Since then, the Iraqi military has steadily pushed ISIS back, shrinking the territory it holds. Over the past eight months the military has clawed its way deeper into the country's second-largest city, which for years has served as one of the pillars of the Islamic State's territorial claims.

The battle for Mosul has reached what Iraqi authorities believe is the final push, as door-to-door fighting consumes the narrow, densely packed streets of the Old City — the last area of Mosul to be occupied by ISIS fighters.

"We will keep following Daesh until we kill and capture the last member in Iraq," Prime Minister Haider al-Abadi said in a statement, referring to ISIS by its acronym in Arabic.

Still, a complete victory remains unfinished for Iraqi troops, which are getting air and logistical support from a U.S.-led coalition. Reuters reports that ISIS militants control less than 1 percent of the city at this point, but reclaiming that area of the city could be difficult because of its layout.

At the same time, an uncertain fate awaits the residents who have been displaced from the city. "Many difficult months lie ahead for the more than 1 million people that were forced to flee their homes, as well as those that remained in Mosul, and survived ISIS brutality and the fight to retake the city," Wendy Taeuber, Iraq country director for the International Rescue Committee, said in a statement.

"Despite the declaration, ISIS still controls some areas in the Old City of Mosul and ongoing fighting will continue to threaten the lives of civilians," she said.

Beyond the battle and even outside Mosul's city limits, another challenge remains, according to West Point's Combating Terrorism Center. The organization released a study Thursday on ISIS' "self-reported military activities in 16 cities" in Iraq and Syria — and it cautions that many of the factors that led to the extremist group's rise persist in those two countries.

"This report is not intended to diminish the gains being won on the battlefield by mostly local forces, supported by a variety of external actors," the research center says.

"What this report suggests is that pushing the Islamic State out as the formal governing party in a territory is not a sufficient development when it comes to ending the group's ability to enact violence against individuals in Iraq and Syria," the report adds.

Despite the conclusive connotations of the term "liberation," the center says ISIS has demonstrated its "intention and capability to carry out attacks" in liberated cities.

"The idea behind this messaging is two things," Aymenn Jawad al-Tamimi, a research fellow at the Middle East Forum, tells Alison. "One is, 'We'll still remain,' and the second one [is] encouraging people to keep up the fight."